Is the Observational Dark Energy Universe Completely a Coincidence?

In this article, we propose a new cosmological model called ‘fractal cosmology’ based on two postulates that gives a ‘not really’ answer to the question in the title: At any epoch of the universe, for an arbitrary local observer living well below the scale of Hubble horizon, the observational universe centered on this observer appears to be accelerated expanding. The anthropic principle is unnecessary for our current observation of an accelerated expanding universe. We will argue how such a story is qualitatively compatible with the CMB and low-redshift observations on the expansion history. Moreover, fractal cosmology implies four characteristic signals that could substantially distinguish it from the standard \(\Lambda\)CDM cosmology and a family of models alike: 1) Unlike the prediction in \(\Lambda\)CDM, in fractal cosmology, the local Hubble rate will be positively correlated with regional matter overdensities. 2) In a conventional expansion history data analysis of modern cosmology, effectively, dynamical dark energy will show phantom behavior. 3) Over-aged high-redshift astronomical objects/events will generally exist, where ‘over-aged’ specifically means that the astronomically (local physics) derived event age is longer than the \(\Lambda\)CDM predicted universe age at the event redshift. 4) Astronomical events with a characteristic time, for example the supernovae light curves, are subject to a growing characteristic time scattering (variance) with their redshifts, even after being modulated by the (\(1+z\)) factor expected in standard cosmology; On the contrary, in for example \(\Lambda\)CDM, no known effect would lead to such a redshift-dependent trend of the characteristic time variance of the same type of events. Each of those four signals has either inconclusively shown some hints in recent observation, or is feasible to be tested with current and near-future available data.